Rheological benchmark of silicone oils used for analog modeling of short- and long-term lithospheric deformation

Abstract

Analog models of tectonic processes at various scales commonly use silicone polymers to simulate viscous flow in the lower crust and mantle. To achieve dynamic similarity with the natural prototype and to improve comparability between analog models, better knowledge of the rheology of commonly used silicones is required. In this study, we present a rheological benchmark of silicones used in various laboratories. Rheometric tests, including rotational and oscillatory tests, were performed and the viscoelastic behavior of silicone is quantitatively described. We found that silicone oils show a transition from Newtonian viscous to power-law, shear thinning behavior around shear rates of 10− 2 to 10− 1 s− 1. The viscosity of chemically similar silicones varied between 2 and 3 × 104 Pa s. Maxwell relaxation times are about 0.1–0.2 s. Such a behavior is able to mimic slow to fast deformation mechanisms in the ductile regime, such as diffusion and dislocation creep as well as viscoelastic relaxation processes. Temperature and aging effects are verified, but can be considered minor with respect to the uncertainty in rheological properties in the natural prototype. Nevertheless, to assure comparability between models and proper scaling the exact properties and conditions should be reported.